pub fn test() {
    let long_binding = 1;
    {
        let short_binding = 2;
        println!("inner short: {}", short_binding);
        let long_binding = 3;
        println!("inner long: {}", long_binding);
    }
    //println!("outer short: {}", short_binding); 报错
    println!("outer long: {}", long_binding);
    let long_binding = 'a';
    println!("outer long: {}", long_binding);
}
